Insulin is known to stimulate protein synthesis and mRNA, but its specific effects on growth hormone (GH) and prolactin (PRL) secretion have not been extensively studied. Insulin receptors on pituitary cells have been described in preliminary reports, and this proposal aims to study the in vitro regulation of PRL and GH release, synthesis and specific mRNA by insulin. Preliminary data demonstrates that insulin at physiological doses suppressed GH secretion and stimulates PRI secretion. The significance of the proposed project is that it will provide information on insulin action on polypeptide hormone synthesis and gene expression. These studies will provide insight into the etiology of elevated GH levels in uncontrolled diabetes. Patients with uncontrolled diabetes have elevated basal and exercise-induced GH levels, and GH has been implicated in the development of diabetic microvascular disease and retinopathy.